Self-Assembled Chiroptical Nanocomposites and Metamaterials for Extreme Conditions

Chiral nanostructures is a large and rapidly evolving class of metamaterials with strong chiroptical activity. Unlike the traditional binary chirality of L/D amino acids and other small biomolecules, the self-assembled nanocomposites display the continuum of chiral states identifiable by continuously variable optical activity. Also important, the chiral nanocomposites have intense polarization rotation in the near- and far-infrared parts of the spectrum, where traditional organic and inorganic compounds display weak dichroism in both absorption and emission. In this talk the problem of highly optically active and highly thermally stable chiroptical materials will be addressed based on the self-assembled nanocomposites. Three types of chiroptically active nanocomposites will be considered. (1) Nacre-like nanocomposites engineered layer-by-layer assembly from MXEnes, MoS₂ nanosheets, and graphene oxide. Their chiroptical activity originates from combination of linear birefringence and linear dichroism. These composites exhibit high polarization rotation in visible and near-infrared parts of the spectrum. They display thermal resilience in the temperature range up to 300 deg C exceeding the upper limit of the stability window of liquid crystals by ~200 degrees. This work was carried out in collaboration with scientists from Air Force Research Laboratory. (2) Chiral nanocomposites based on twisted carbon filaments. These nanostructured metamaterials exhibit bright black-body radiation with strong temperature dependent chiroptical activity in visible, near-infrared and far-infrared parts of the spectrum. The carbon-silica nanocomposites display record high temperature stability up to 120 deg C. (3) Composites based on the nanostructured kirigami sheets with twisted shapes. The chiroptical peaks are located in the far-infrared terahertz region of the spectrum. They display extremely sharp and strong peaks with amplitude exceeding those typically observed for organic materials by ~1000 times. This project is carried out in collaboration with researchers from Lawrence Livermore National Laboratory.
The continuous dependence of chiroptical activity on chirality measures was observed, which simplifies their rapid ‘tuning’ to the necessary spectral band. The manufacturing methods with high degree of scalability were demonstrated for all types of temperature-resilient chiral nanocomposites listed above.